Metal recovery apparatus and method

ABSTRACT

Apparatus and a method for removing a metal from solutions, such as silver from a hypo solution, wherein the solution is caused to circulate in a closed fluid circuit containing a globular space across which a potential gradient is maintained, thus causing a current flow when the solution flows through the space, whereby metal is separated from the solution by an electrolytic action. Access to the space can be had to retrieve the recovered metal and the process can be automated to minimize manual functions.

0 United States Patent [151 3,658,683 Lagier et al. 1 Apr. 25, 1972 54]METAL RECOVERY APPARATUS AND 3,524,805 8/1970 Engelman ..204/228 METHOD3,551,318 12/1970 Snook et al... ..204/228 1,885,702 11/1932 Fink....204/229 X [72] Invent: if gg i fizf 3,361,663 l/l968 Murray et a1....'.204/278 a 1 3,385,779 5/1968 Nishiba et al..... ....204/272 [73]Assignee: Ornnific Research and Development 3,468,775 9/1969 Lanning eta1. ..204/228 X Center, Inc., Mountain View, Calif. Primary Examiner-F.C. Edmundson [22] Filed May 1970 Attorney-Townsend and Townsend [21]App1.No.: 33,760

[57] ABSTRACT [52] U.S. Cl ..204/272, 204/275, 204/278, Apparatus and amethod f removing a meta] f solutions, 204/109, 204/229 such as silverfrom a hypo solution, wherein the solution is [51] Int. Cl. ..B0lk 1/00,C231) 5/00 caused to circume i a l d fl id circuit containing a globu-[58] Fleld of Search ..204/22823l, 272, l space across which a potentialgradient is maintained, thus 204/275 278 causing a current flow when thesolution flows through the space, whereby metal is separated from thesolution by an [56] References cued electrolytic action. Access to thespace can be had to retrieve UNITED STATES PATENTS the recovered metaland the process can be automated to minimize manual functions. 1,251,30212/1917 Toirrton ..204/l10 3,510,413 5/1970 Lindau ..204/l09 13 Claims,3 Drawing Figures CURRENT REGULATOR CONTROLLER E. ER

STEPPER SWITCH FILL R mum Patented April 25, 1972 3,658,683

3 Sheets-Sheet 1 INVENTORS 5 GARYGLACIER E RAYMOND LFUESS ATTORNFYS 7Patented April 25, 1972 3 Sheets-Sheet 2 INVENTORS 'GARYGLAGIER RAYMONDLFUESS ATTORNEYS Patented April 25, 197 2 3 Sheets-Sheet 8 v kl 5 55 wINVENTORS GARY e. LAGIER RAYMONDLFUESS ATTORNEYS METAL RECOVERYAPPARATUS AND METHOD This invention relates to improvements in therecovery of metals from solutions and, more particularly, to apparatusand a method for more effectively recovering a metal, such as silver orthe like, from a circulating solution.

While the present invention is suitable for the recovery of differenttypes of metals in solutions, it is especially suitable for use inrecovering silver from hypo solutions, a task which has utilized anumber of different types of apparatuses and methods in the past. All ofthe conventional techniques of silver recovery are satisfactory but eachhas its drawbacks for one reason or another. The present inventionprovides an apparatus and method which increases the efficiency ofsilver recovery over that attained with conventional techniques andutilizes a globular space for receiving solution from which metal is tobe recovered with the space being bounded by positive and negativeelectrodes to establish a potential gradient across which the solutionpasses as it circulates through the space, whereby current flows fromone electrode to the other and the metal can be plated or deposited ontothe negative electrode by an electrolytic action.

The apparatus of the invention includes a globular unit which enclosesthe space for receiving the solution containing the metal to berecovered. The globular unit also defines the negative electrode orcathode of the electrical circuit and the anode or positive electrode ismounted at the center of the globular unit to provide a substantiallyconstant current density which can more easily control the electrolyticaction. Moreover, the globular construction which provides maximumplating area or surface on which the metal to be recovered can bedeposited for a given volume of space. The globular unit can be groundedso as to minimize injuries due to electrical shocks and, since the unititself defines the cathode, no additional structure is needed to formthis element of the circuit.

Another feature of the invention is the improved fluid circuitry whichallows substantially uninterrupted circulation of the solution throughthe globular space after the latter has been filled to a predeterminedlevel. With such a circuit, it is possible to achieve maximum separationof a metal from a solution in a given amount of time. The fluidcircuitry can be automatically controlled by the use of sensors atvarious locations in the circuitry itself. Thus, manual functionsrequired to operate the apparatus can be significantly minimized.

Still a further feature of the invention is the capability ofcontrolling the electrical current for causing the deposition of metalon the cathode as well as controlling the volume rate of flow of thesolution through the globular space. In this way, more effective controlof the electrolytic action can be realized so as to assure maximumefficiency in the separation of metal from a solution.

The primary object of this invention is to provide an apparatus andmethod for separating a metal from a solution wherein the solution isdirected through a globular space across which a potential gradient isestablished so that the metals can be deposited by an electrolyticaction on a surface at one boundary of the space as the solutioncirculates therethrough.

Another object of this invention is to provide apparatus and a method ofthe type described wherein the globular space has a substantiallyspherical inner surface on which the metal to be separated is deposited,whereby the surface provides the maximum plating area for a given volumeof space through which the solution circulates and the deposited metalcan be retrieved by gaining access to the globular space.

Still a further object of this invention is to provide an apparatus andmethod of the aforesaid character which permits either the currentdensity in the space or the volume rate of flow of solution through thespace to be varied so as to provide greater control of the electrolyticaction and thereby achieve a more efiicient separation of a metal from asolution flowing through the space itself.

Other objects of this invention will become apparent as the followingspacification progresses, reference being had to the accompanyingdrawings for an illustration of an embodiment of the apparatus.

In the drawings:

FIG. 1 is a side elevational view of the metal-recovery apparatus ofthis invention, parts being broken away to illustrate details ofconstruction;

FIG. 2 is an enlarged, fragmentary, side elevational view, partly insection and partly broken away, of the metalrecovery chamber of theapparatus; and

FIG. 3 is a schematic diagram of the apparatus including the fluidcircuitry and the controlling means thereof.

The metal-recovery apparatus which is the subject of this invention isbroadly denoted by the numeral 10 and includes a globular recovery unit12 mounted in an operative position on a housing 14 (FIG. 1) ofelectrically non-conducting material, the housing adapted to besupported on a surface, such as a floor or the like. Housing 14 has aninclined face 16 which provides a control panel for controls connectedto the operating portions of the apparatus. For purposes ofillustration. FIG. 1 shows a control knob 18 and a number of panellights 20 for indicating various operative conditions of apparatus 10.

Unit 12 is shown in more detail in FIG. 2 and includes a pair ofsemi-spherical halves or members 22 and 24 having respective outerperipheral flanges 26 and 28 which mate with each other so that themembers define a globular construction. A number of fasteners 30(FIG. 1) are used to interconnect flanges 26 and 28 whereby toreleasably secure member 22 to member 24. Preferably, member 24 isrigidly secured to housing 14 and extends inwardly thereof as shown inFIG. 1. Thus, to gain access to the interior of unit 12, fasteners 30are manipulated so that member 22 can be separated from member 24.

Members 22 and 24 are formed from a suitable electrically conductingmaterial, such as stainless steel or the like. The members have smoothinner surfaces and define the negative electrode or cathode of anelectrical circuit which is used to separate a metal by an electrolysisaction from a solution moving through unit 12. Thus, when a particularmetal has been deposited by an electrolytic action on the inner surfacesof members 22 and 24, the metal can be recovered by separating member 22from member 24 so as to gain access to the interior of unit 12. Themetal can then be removed from the members in any suitable manner.

Member 24 has a lowermost, cup-shaped projection 32 which communicatestherewith and defines a drain means for unit 12. A pipe 34, only aportion of which is shown in FIG. 2, extends laterally from projection32 and communicates with the interior of member 24 to carry off drainedliquid therefrom. Member 24 also has a pipe 36 communicating with theinterior thereof and defining a fluid inlet therefor. Only a portion ofpipe 36 is shown in FIG. 2. Thus, liquid entering pipe 36 can flowthrough unit 12 and out of the same through pipe 34. Pipe 36 has aninterior nozzle (not shown) which is positioned so that fluid enteringunit 12 will be directed along a path to the axis of pipe 36 tangent toa circuit surrounding the central axis of unit 12, whereby the fluidwill be caused to circulate through unit 12 as it is pumped thereinto.In this way, the fluid will be actively moved through the units toassure a more efiective separation of a metal from the solution byelectrolytic action.

Projection 32 is formed from an electrically non-conducting material;thus, it is not an integral part of member 24. It is fitted within ahole in the bottom of the member and has an annular upper portion 38which rests on the inner surface of member 24 which surrounds the hole.An annular seal 40 is provided to seal the junction between member 24and pro jection 32.

Projection 32 has a central tubular extension 42 which extends upwardlyand into member 24 and provides a support for an electrically conductingpipe 44 which supports the anode 46 of unit 12. Pipe 44 has a conical,outer surface 48 which is complemental to the inner surface 50 of a boreextending through anode 46. The purpose of this conical shape is toprovide a limiting means for holding anode 46 against downward movementbeyond a certain distance along pipe 44 and to provide adequateelectrical contact.

Anode 46 is formed from any suitable material, such as carbon or thelike. It is in electrical contact with pipe 44. The shaft is surroundedby a suitable non-conductive sheath 54 in the region between the bottomextremity of anode 46 and the upper extremity of extension 42. Pipe 44extends downwardly and outwardly of projection 32 and has a lug 56thereon by means of which electrical contact can be made with pipe 44and thereby anode 46.

A tube 56 of electrically conductive material is disposed within pipe 44and is longer than the latter. Tube 56 is supported by bushings 66 inpipe-44, the bushings being made from a non-conductive material. Tube 56has an open upper end 58 and a lateral lower portion 60 and operates tovent unit 12 to the atmosphere when a solution is directed thereinto.The upper portion of tube 56 is used to sense liquid level in unit 12.An insulating sheath 68 extends upwardly from upper bushing 66 to permitonly a limited surface area of shaft 56 to be exposed. Tube 56 alsoallows air to enter unit 12 when the solution is drained therefrom.

Members 22 and 24 are electrically connected by conductors (not shown)to a current regulator 70 (FIG. 3) which receives electrical power froman external'power source. Current regulator 70 is used to maintain acurrent output proportional to a command signal received when thecurrent output is above a predetermined minimum value. When the currentoutput is below this predetermined value or if current regulator 70receives the appropriate command, the output of the current regulator isblocked.

The fluid circuitry of apparatus is illustrated in FIG. 3 and includes afluid inlet line 72 which is adapted to be connected to a fluid sourcesuch as a receptacle containing a solution having a quantity of silverto be recovered. Line 72 is connected to the inlet of a fluid pump 74whose outlet is connected to an outlet line 76, the latter adapted to beconnected to a fluid disposal means, such as a sewer line or the like.lnlet pipe 36 is coupled to outlet line 76 and outlet pipe 34 isconnected to inlet line 72. Thus, pump 74 is disposed between pipes 34and 36. A normally closed valve 82 is coupled across inlet line 72 and anormally closed valve 84 is coupled across outlet line 76. Normally openvalves 86 and 88 are. coupled with pipes 36 and 34, respectively. Pump74 is used to fill unit 12 with a solution, circulate the solutiontherethrough, and drain the solution therefrom.

A controller 90 is provided to accept command signals from sensors to bedescribed and, by means of such signals, to control current regulator70, pump 74 and a stepper switch 94, all of which are electricallyacuated and are electrically coupled by lead means to be described. Leadmeans 92 couples controller 90 with pump 74; lead means 95 couplescontroller 90 to stepper switch 94; and lead means 97 couples controller90 with current regulator 70.

Stepper switch 94 operates to accept command signals and power fromcontroller 90, to furnish output power to valves 82, 84, 86 and 88, andto provide an operating signal to controller 90 by way of lead means 99.Stepper switch 94 has a fill position 96 and is connected by lead means98 to valves 82 and 88. It also has a drain position 100 connected bylead means 102 to valves 84 and 86. The stepper switch serves asequencing and memory function and steps through three positions,namely, fill, recovery or separation and drain.

A fluid inlet sensor 112 in inlet line 72 is coupled with controller 90through lead means 114. Sensor 112 provides an indication when a fluidis flowing through inlet line 72 toward pump 74.

An outlet sensor 116 is disposed in outlet line 76 and is coupled bylead means 118 to controller 90. Sensor 116 provides an indication whenfluid is flowing through outlet line 76. A sensor 120 is disposed withinunit 12 and is connected by lead means 122 to controller 90. Sensor 120indicates the level of the fluid withinunit 12.

A solution condition sensor is disposed in pipe 36 and is coupled bylead means 136 to current regulator 70. This sensor provides a controlsignal by means of which a command can be directed to the currentregulator to cause it to supply a current depending upon theconcentration of a metal in the solution circulating through unit 12.

In operation, apparatus 10 is connected in the manner shown in FIG. 3with inlet line 72 coupled to a source of liquid having a metal in thesolution, such as a hypo solution containing silver to be retrieved.Valves 82 and 84 will normally be closed and valves 86 and 88 willnormally be open. Outlet line 76 will be coupled to a fluid disposalmeans.

Stepper switch 94 is manually set to the fill position and controller isgiven a start command. These actions cause the opening of valve 82, theclosing of valve 88, and the supply of power to current regulator 70 andcontroller 90. When this occurs, pump 74 is actuated and the solutionliquid is caused to flow into unit 12 and to fill the same to apredetermined level as determined by sensor 120. When this level hasbeen reached, a signal will be sent from sensor to controller 90 whichwill advance switch 94 to the recover position to operate to close valve82 and open valve 88.

Pump 74 will continue to operate and as it does, it causes the solutionto circulate in the closed circuit including the following: pump 74,pipe 78, valve 86, pipe 36, unit 12, pipe 34, valve 88, and pipe 80. Theliquid enters unit'12 in a direction to cause circulation of the liquidtherewithin. When stepper switch 94 goes into the recover position,current regulator 70 establishes the potential gradient across the spacebetween the electrodes of unit 12 and thereby supplies a maximum currentthereto proportional to the signal from solution condition sensor 124.This operating mode continues until current in unit 12 falls below theaforesaid predetermined minimum value.

As the solution circulates within unit 12, the metal in the solutionwill be removed therefrom and deposited on the inner surfaces of members22 and 24.

When the predetermined minimum current value has been reached, a signalfrom current regulator 70 is directed by lead means 97 to controller 90which, in turn, advances stepper switch 94 to the drain position 100.Valve 84 is then opened and valve 86 is closed, whereupon pump 74continues to operate to empty unit 12 of solution and to direct thesolution through outlet line 76. Sensor 116 directs a control signal tocontroller 90 when line 76 is empty to thereby cause the controller toadvance the stepper switch back to the fill position 96. The operatingsequence can then be repeated to recover metal from a second volume ofthe solution.

If sensor 112 indicates no solution passing through inlet line 72 whenstepper switch 94 is in the fill position, controller 90 falls into arelease mode and all power to control valves 82, 84, 86 and 88 isremoved. Also, power to pump 74 is removed. When the source of thesolution is replenished, controller 90 is manually given a reset signaluntil the fill line is primed; then, normal, automatic batch processingwill continue.

To facilitate the connection of inlet pipe 72 and outlet pipe 76,apparatus 10 is provided with side openings as shown in FIG. 1 toconnect the inlet and outlet pipes 72 and 76 directly to the source ofsolution and the fluid disposal means, respectively. Lateral portion 60of tube 56 is also disposed adjacent to the connections for inlet andoutlet pipes 72 and 76.

What is claimed is: v

1. Apparatus for recovering a metal from a solution by an electrolyticaction comprising: a fluid circuit including a fluid receiving unitdefining a generally spherical space, with the unit being of anelectrically conductive material to define a first electrode and valvemeans coupled with said fluid circuit for controlling the flow of asolution into, through and out of the unit; means defining a secondelectrode within the unit; means coupled with said unit and insulatedtherefrom for supporting said second electrode, whereby a potentialgradient can be established across said space to permit an electricalcurrent to flow between the electrodes; means coupled with theelectrodes for establishing a potential gradient therebetween; and meanscoupled with the valve means for actuating the same in accordance with apredetermined sequence.

2. Apparatus as set forth in claim 1, wherein said unit comprises a pairof generally semi-spherical members, and means on said members forreleasably interconnecting the same,

3. Apparatus as set forth in claim 1, wherein is provided means forventing the space as a solution is directed thereinto.

4. Apparatus as set forth in claim 1, wherein said fluid circuitincludes a fluid pump, there being an inlet line connected to the inletof the pump and an outlet line connected to the outlet of the pump, anda pair of valves coupled to the pump at the inlet and outlet thereof,respectively, said valves being controlled by said controlling means tocooperate with said valve means to control the flow of a solution into,through and out of said circuit.

5. Apparatus as set forth in claim 1, wherein said electrode issubstantially equally spaced from all locations on said inner surface ofthe unit.

6. Apparatus as set forth in claim 1, wherein is included a tubularshaft carried by the unit and extending into the space, the inner end ofthe shaft being open to vent the interior of the unit to a regionexteriorly thereof, said second electrode being mounted on the shaftcentrally of the unit.

7. Apparatus as set forth in claim 1, wherein is included means coupledwith the unit for sensing the level of solution in said space.

8. ln apparatus for recovering a metal from a solution by anelectrolytic action: a fluid-receiving unit having a generally sphericalinner surface and being formed from an electrically conductive material;an electrode which is substantially equally spaced from all locations onsaid inner surface of said unit; and means coupled with the unit andelectrically insulated therefrom for mounting the electrode within thespace, there being conductor means for connecting the electrode to asource of electrical power.

9. An apparatus as set forth in claim 8, wherein said mounting meansincludes a pipe, and means securing the pipe to the unit and maintainingthe pipe out of electrical contact therewith.

10. An apparatus as set forth in claim 9, wherein the pipe has an openinner end disposed adjacent to the upper extremity of the space to ventthe same to a region externally of the unit.

11. An apparatus as set forth in claim 8, wherein said unit includes apair of generally semi-spherical members, and means on the members forreleasably interconnecting the same.

12. Apparatus for recovering a metal from a solution by an electrolyticaction comprising: a fluid circuit including a closed, fluid-receivingunit having a generally spherical inner space and defining a firstelectrode, an inlet pipe and an outlet pipe coupled with the unit, saidinlet and outlet pipes being coupled with the outlet and inlet,respectively, of a fluid pump; a valve for each of the inlet and outletpipes, respectively; inlet means coupled with the inlet of the pump forcontrollably directing a solution thereto; outlet means coupled with theoutlet of the pump for controllably directing a solution away from thecircuit; a second electrode; means mounting the second electrode at acentral location within the space; means coupled with the electrodes forestablishing a potential gradient therebetween; and means coupled withthe valves for actuating the same to cause a solution to be directedinto the circuit, to circulate therethrough, and be discharged therefromin accordance with a predetermined sequence.

13. Apparatus as set forth in claim 12, wherein is provided a firstsensor coupled with the inlet means, a second sensor coupled with theoutlet means, sand a third sensor coupled with said fluid circuit, saidsensors being connected to said controlling means for actuating the samein accordance with said sequence.

2. Apparatus as set forth in claim 1, wherein said unit comprises a pairof generally semi-spherical members, and means on said members forreleasably interconnecting the same.
 3. Apparatus as set forth in claim1, wherein is provided means for venting the space as a solution isdirected thereinto.
 4. Apparatus as set forth in claim 1, wherein saidfluid circuit includes a fluid pump, there being an inlet line connectedto the inlet of the pump and an outlet line connected to the outlet ofthe pump, and a pair of valves coupled to the pump at the inlet andoutlet thereof, respectively, said valves being controlled by saidcontrolling means to cooperate with said valve means to control the flowof a solution into, through and out of said circuit.
 5. Apparatus as setforth in claim 1, wherein said electrode is substantially equally spacedfrom all locations on said inner surface of the unit.
 6. Apparatus asset forth in claim 1, wherein is included a tubular shaft carried by theunit and extending into the space, the inner end of the shaft being opento vent the interior of the unit to a region exteriorly thereof, saidsecond electrode being mounted on the shaft centrally of the unit. 7.Apparatus as set forth in claim 1, wherein is included means coupledwith the unit for sensing the level of solution in said space.
 8. Inapparatus for recovering a metal from a solution by an electrolyticaction: a fluid-receiving unit having a generally spherical innersurface and being formed from an electrically conductive material; anelectrode which is substantially equally spacEd from all locations onsaid inner surface of said unit; and means coupled with the unit andelectrically insulated therefrom for mounting the electrode within thespace, there being conductor means for connecting the electrode to asource of electrical power.
 9. An apparatus as set forth in claim 8,wherein said mounting means includes a pipe, and means securing the pipeto the unit and maintaining the pipe out of electrical contacttherewith.
 10. An apparatus as set forth in claim 9, wherein the pipehas an open inner end disposed adjacent to the upper extremity of thespace to vent the same to a region externally of the unit.
 11. Anapparatus as set forth in claim 8, wherein said unit includes a pair ofgenerally semi-spherical members, and means on the members forreleasably interconnecting the same.
 12. Apparatus for recovering ametal from a solution by an electrolytic action comprising: a fluidcircuit including a closed, fluid-receiving unit having a generallyspherical inner space and defining a first electrode, an inlet pipe andan outlet pipe coupled with the unit, said inlet and outlet pipes beingcoupled with the outlet and inlet, respectively, of a fluid pump; avalve for each of the inlet and outlet pipes, respectively; inlet meanscoupled with the inlet of the pump for controllably directing a solutionthereto; outlet means coupled with the outlet of the pump forcontrollably directing a solution away from the circuit; a secondelectrode; means mounting the second electrode at a central locationwithin the space; means coupled with the electrodes for establishing apotential gradient therebetween; and means coupled with the valves foractuating the same to cause a solution to be directed into the circuit,to circulate therethrough, and be discharged therefrom in accordancewith a predetermined sequence.
 13. Apparatus as set forth in claim 12,wherein is provided a first sensor coupled with the inlet means, asecond sensor coupled with the outlet means, sand a third sensor coupledwith said fluid circuit, said sensors being connected to saidcontrolling means for actuating the same in accordance with saidsequence.